Ethanol sensitivity of the GABAA receptor expressed in xenopus oocytes requires 8 amino acids contained in the γ2L subunit

Wafford, Keith A.; Burnett, Donald M.; Leidenheimer, Nancy J.; Burt, David R.; Wang, Jia Bei; Kofuji, Paulo; Dunwiddie, Thomas V.; Harris, R. Adron; Sikela, James M.

doi:10.1016/0896-6273(91)90071-7

Cited by 347 publications

(130 citation statements)

References 21 publications

Supporting

Mentioning

125

Contrasting

Unclassified

Order By: Relevance

“…The indirect modulation might involve protein phosphorylation, either of GABA A R protein or another protein (Harris et al, 1995). The first possibility was supported by the 'γ2 L subunit' hypothesis (Wafford et al, 1991), which is now considered unlikely (Sigel et al, 1993;Marszalec et al, 1994;Homanics et al, 1999;Wallner et al, 2003). The second hypothesis was also potentially related to the γ2 L splice variant, since it differed from γ2 S having added an 8-amino acid insert containing a protein kinase C (PKC) substrate site.…”

Section: Evidence For Low Concentration Alcohol Enhancement Of Gaba Amentioning

confidence: 65%

Low dose acute alcohol effects on GABAA receptor subtypes

Wallner

Hanchar

Olsen

2006

Pharmacology & Therapeutics

View full text Add to dashboard Cite

GABA A receptors (GABA A Rs) are the main inhibitory neurotransmitter receptors and have long been implicated in mediating at least part of the acute actions of ethanol. For example, ethanol and GABAergic drugs including barbiturates and benzodiazepines share many pharmacological properties. Besides the prototypical synaptic GABA A R subtypes, nonsynaptic GABA A Rs have recently emerged as important regulators of neuronal excitability. While high doses (≥100 mM) of ethanol have been reported to enhance activity of most GABA A R subtypes, most abundant synaptic GABA A Rs are essentially insensitive to ethanol concentrations that occur during social ethanol consumption (<30 mM). However, extrasynaptic δ and β3 subunit-containing GABA A Rs, associated in the brain with α4or α6 subunits, are sensitive to low millimolar ethanol concentrations, as produced by drinking half a glass of wine. Additionally, we found that a mutation in the cerebellar α6 subunit (α6R100Q), initially reported in rats selectively bred for increased alcohol sensitivity, is sufficient to produce increased alcohol-induced motor impairment and further increases of alcohol sensitivity in recombinant α6β3δ receptors. Furthermore, the behavioral alcohol antagonist Ro15-4513 blocks the low dose alcohol enhancement on α4/6/β3δ receptors, without reducing GABA-induced currents. In binding assays α4β3δ GABA A Rs bind [ 3 H] Ro15-4513 with high affinity, and this binding is inhibited, in an apparently competitive fashion, by low ethanol concentrations, as well as analogs of Ro15-4513 that are active to antagonize ethanol or Ro15-4513's block of ethanol. We conclude that most low to moderate dose alcohol effects are mediated by alcohol actions on alcohol/Ro15-4513 binding sites on GABA A R subtypes.

show abstract

Section: Evidence For Low Concentration Alcohol Enhancement Of Gaba Amentioning

confidence: 65%

Low dose acute alcohol effects on GABAA receptor subtypes

Wallner

Hanchar

Olsen

2006

Pharmacology & Therapeutics

View full text Add to dashboard Cite

show abstract

“…In an initial study, Wafford et al (1991) found that when various sets of GABA A subunits were assembled in oocytes, only that combination containing the a 1 b 1 g 2L subunits was affected by ethanolFa finding confirmed in L(tk À ) cells (Harris et al, 1995c). Additionally, Harris et al (1997) found that ethanol enhanced muscimol-induced chloride flux in L(tk À ) cells transfected with a 1 b 2/3 g 2L GABA A receptor subunits.…”

Section: Hypothesis For Ethanol Action On a Type-1-bzd Receptormentioning

confidence: 93%

“…Most important to the concept that zolpidem predicted the action of ethanol on GABA function , ethanol at reasonable concentrations did not alter the effect of GABA responsiveness when the a 1 b 2 g 2L combination was expressed in various cell lines (see Criswell et al, 2003;Kleingoor et al, 1991;Mihic et al, 1994;Mori et al, 2000;Sapp and Yeh, 1998;Sigel et al, 1993) or in oocytes (Harris et al, 1997)Fa contrast to the positive effect found when the a 1 b 1 g 2L subunit combination was expressed in oocytes (Wafford et al, 1991) or L(tk À ) cells (Harris et al, 1995c). Consequently, the view concerning the specificity for ethanol to affect the type-1-BZD receptor directly to enhance GABA function was placed in doubt.…”

Section: In Vitro Examination Of Ethanol Action On Gaba a Receptor Fumentioning

confidence: 99%

A Conceptualization of Integrated Actions of Ethanol Contributing to its GABAmimetic Profile: A Commentary

Criswell

Breese

2005

Neuropsychopharmacol

View full text Add to dashboard Cite

Early behavioral investigations supported the contention that systemic ethanol displays a GABAmimetic profile. Microinjection of GABA agonists into brain and in vivo electrophysiological studies implicated a regionally specific action of ethanol on GABA function. While selectivity of ethanol to enhance the effect of GABA was initially attributed an effect on type-1-benzodiazepine (BZD)-GABA A receptors, a lack of ethanol's effect on GABA responsiveness from isolated neurons with this receptor subtype discounted this contention. Nonetheless, subsequent work identified GABA A receptor subtypes, with limited distribution in brain, sensitive to enhancement of GABA at relevant ethanol concentrations. In view of these data, it is hypothesized that the GABAmimetic profile for ethanol is due to activation of mechanisms associated with GABA function, distinct from a direct action on the majority of postsynaptic GABA A receptors. The primary action proposed to account for ethanol's regional specificity on GABA transmission is its ability to release GABA from some, but not all, presynaptic GABAergic terminals. As systemic administration of ethanol increases neuroactive steroids, which can enhance GABA responsiveness, this elevated level of neurosteroids is proposed to magnify the effect of GABA released by ethanol. Additional factors contributing to the degree to which ethanol interacts with GABA function include an involvement of GABA B and other receptors that influence ethanol-induced GABA release, an effect of phosphorylation on GABA responsiveness, and a regional reduction of glutamatergic tone. Thus, an integration of these consequences induced by ethanol is proposed to provide a logical basis for its in vivo GABAmimetic profile.

show abstract

“…One report claimed that the γ2L splice variant would generate GABA A Rs with high alcohol sensitivity (Wafford et al, 1991). Numerous studies showed that receptors containing either the short (γ2S) or and the long (γ2L) γ2 splice variant are enhanced by alcohol (Sigel et al, 1993;Wallner et al, 2003), but both only at concentrations >60 mM, within the range of deadly concentrations in humans but not at lower, mildly intoxicating levels.…”

Section: Gaba a Receptors As Plausible Alcohol Targetsmentioning

confidence: 99%

GABAA receptor subtypes: the “one glass of wine” receptors

Olsen

Hanchar

Meera

et al. 2007

Alcohol

127

121

View full text Add to dashboard Cite

This review discusses evidence for and apparent controversy about, GABA A receptor subtypes that mediate alcohol effects experienced during social drinking. GABA A receptors that contain the β3 and δ subunits were shown to be enhanced by alcohol concentrations that mirror the concentrationdependence of alcohol responses in humans. A mutation (α6R100Q) previously found in alcohol non-tolerant (ANT) rats in the cerebellar GABA A receptor α6 subunit is sufficient for increased alcohol-induced ataxia in rats homozygous for this mutation (α6-100QQ) and further increases alcohol-sensitivity of tonic GABA currents (mediated by α6βδ receptors) in cerebellar granule cells of α6-100QQ rats and in recombinant α6R100Qβ3δ receptors. This provided the first direct evidence that these types of receptors mediate behavioral effects of ethanol. Furthermore the behavioral alcohol antagonist Ro15-4513 specifically reverses ethanol enhancement on α4/6β3δ receptors. Unexpectedly, native and recombinant α4/6β3δ receptors bind the behavioral alcohol antagonist Ro15-4513 with high affinity and this binding is competitive with EtOH, suggesting a specific and mutually exclusive (competitive) ethanol/Ro15-4513 site which explains the puzzling activity of Ro15-4513 as a behavioral alcohol antagonist.Our conclusion from these findings is that alcohol/Ro15-4513-sensitive GABA A receptor subtypes are important alcohol targets and that alcohol at relevant concentrations is more specific than previously thought. In this review we discuss technical difficulties in expressing recombinant δ subunit-containing receptors in oocytes and mammalian cells, that may have contributed to negative results and confusion. Not only because we have reproduced detailed positive results numerous times, and we and many others have built extensively on basic findings, but also because we explain and combine many previously puzzling results into a coherent and highly plausible paradigm on how alcohol exerts an important part of its action in the brain, we are confident about our findings and conclusions. However, many important open questions remain to be answered.

show abstract

Ethanol sensitivity of the GABAA receptor expressed in xenopus oocytes requires 8 amino acids contained in the γ2L subunit

Cited by 347 publications

References 21 publications

Low dose acute alcohol effects on GABAA receptor subtypes

Low dose acute alcohol effects on GABAA receptor subtypes

A Conceptualization of Integrated Actions of Ethanol Contributing to its GABAmimetic Profile: A Commentary

GABAA receptor subtypes: the “one glass of wine” receptors

Contact Info

Product

Resources

About